1. Field of the Invention
The present invention relates to signal tracking. More particularly, the invention relates to a method and apparatus for all-polarization direction finding that utilizes signal measurements provided by a blind signal extraction algorithm.
2. Description of the Related Art
The ability to determine the source geolocation of emitted signals is becoming increasingly important as the use of wireless communications devices becomes commonplace throughout the world. For example, the U.S. Federal Communications Commission Enhanced 911 (E911) rules will eventually require cellular telephone carriers to identify the geolocations, i.e. the physical source locations, of subscribers who place calls to 911. Additionally, wireless communication device users often desire to acquire accurate geolocations for navigation purposes, such as to generate a route between a current location and a destination. Further, military and law enforcement agencies often desire to locate sources of emitted signals for tracking and targeting purposes.
Methods and devices have been developed that enable signal geolocations to be determined. Some of these methods include utilizing Global Position System (GPS) elements that must be coupled with signal emitters to determine geolocations, thereby increasing system cost and complexity. Other methods include utilizing one or more collector elements, such as antennas, to generate signal measurements and compute geolocations utilizing the generated signal measurements.
Although utilizing signal measurements enables geolocations to be determined without physically interfacing with signal emitters, such methods often require, utilize, or present information concerning the angle of arrival (AOA) of emitted signals. Unfortunately, developed methods of calculating AOA require signals to be exclusively vertically or horizontally polarized or require the use of algorithms such as the multiple signal classification (MUSIC) algorithm. As signals are often not exclusively vertically or horizontally polarized and the MUSIC algorithm requires knowledge of how many signals are in the environment and is generally inoperable to utilize measurements provided by blind signal extraction algorithms, signal tracking methods are often inhibited when faced with diversely polarized signals.